By analogy with the standard theory of unconventional superconductivity,[1]}, [2]} one can consider separately the pairing in the singlet and triplet channels, keeping in mind that the Kramers index \(s\) 
is neither spin nor pseudospin, in general. The matrix structure of the gap functions in the Kramers space can be represented in the following form:
\(\hat{\Delta }_n( {k} )=\psi _n( {k} )\hat{\sigma }_0,\quad \psi _n(- {k} )=\psi _n( {k} ),\) 
